The present invention concerns improvements in continuous shoring machines for tunneling of the type consisting of a load-bearing structure which rests on supporting skids and on which are mounted shoring members for shaping and propping up the tunnel surface.
Until now, the methods used in tunneling have been based on partial excavation of the tunnel portion under construction and immediate shoring up of the said excavated part. Then, once the section worked on is safe, repeating the process until the entire section is excavated and afterwards proceeding to line it with concrete.
These methods, recognized up to now, have the great disadvantage of not being up to the technological level which the other operations, e.g., the excavation and transport of the muck, placing forms, concreting, etc., have reached. For this reason, various procedures have been developed for mechanized excavation which accelerate the work, performing it at high speed and low cost. However, these systems are hindered by the later manual shoring in stages, carried out by outdated methods, impeding the execution of the project in a continuous manner, as if the excavation were not mechanized.
The object of the present invention is to develop a machine which avoids the previous drawbacks, which provides a method of continuous shoring by a special machine across the entire section of the tunnel at the same time, the machine having, moreover, the necessary means for advancing as the work proceeds, as well as the arrangements and mechanisms necessary for controlling this advance and positioning so that at every instant the entire rig is oriented and in perfect contact with the tunnel surface, developing the pressures required for the best progress of its work.
As has been pointed out, the machine consists of a load-bearing structure resting on supporting skids and on which are mounted shores for shaping and shoring up the tunnel surface.
The sturdy frame is formed by two arches, preferably parallel, one in front and one behind, separated by a space sufficient for the requirements of fitting in the various systems and elements of the machine. The arches are firmly connected to one another by suitable bracing members and a platform base, forming a rigid overall structure, the section of which is variable in accordance with the dimensions of the tunnel.
The structure described is that which absorbs the load of supporting the tunnel walls and roof and on which are mounted the other elements.
The rig is furnished with suitable hydraulic circuits with corresponding cylinders for moving the machine forward.
In accordance with the invention, the rig is provided with elastic supports connecting the sturdy frame to the skids and shores, as well as means of guiding the skids vertically and horizontally.
The elastic supports and the means of guiding the skids help to orient the machine in plane and elevation, avoiding an excessive or uncontrolled displacement between the skids and the frame and maintaining the relative positions of the two. That is, the rig is given a firm footing on the tunnel floor, passing over obstacles on it, the machine being aided in its sliding and orientation at all times in following the prescribed course.
For their part, the elastic supports of the shores permit obtaining the following effects.
a. Varying the machine's section with consequent variation of the excavated and shored section, as required;
b. Maintaining the shores in contact with the surfaces to be propped up by means of their controllable position;
c. Guiding the machine in plan and elevation, enlarging the sections according to their orientation and producing a set of pressures for displacing the machine along the assigned course;
d. Increasing the friction forces between the shores and the tunnel surface, with the result that the hydraulic cylinders of each of the shores cause the frame to advance when they are actuated in the direction opposite to their own advancement;
e. Suitably distributing the tensions produced in the shores and equalizing the load transmitted to the two arches.
The supports of the shores are elastic, gradual and variable, and the basic idea of their arrangement is to make the forward arch controllable in order always to keep the shores in contact with the tunnel surface.
The elastic supports connecting the frame to the skids consist of freely rotating rollers with horizontal axes which rest on top of the skids and are each mounted between two lugs pivoted at corresponding ends on; the machine, while at their opposite ends, the said load-bearing frame is supported by the intermediary of a hydraulic cylinder actuated by its corresponding circuit with nitrogen accumulators and corresponding oil reservoirs. Each skid can carry four rollers of this type, two in front and two in back, the various hydraulic circuits being able to cooperate for producing the combinations necessary to compensate for the irregularity of the tunnel floor on either side.
This whole arrangement permits varying the inclination of the skids in a vertical plane with respect to the frame, and with it the height of the frame at its front or back, facilitating the orientation of the machine.
Identical elastic supports but having the rollers turning about vertical axes, are disposed at the sides of the skids for guidance in a horizontal direction, by being able to vary the inclination of the skids in a horizontal plane with respect to the frame and thus changing the orientation of the rig.
For their part, the elastic supports which connect the frame to the shores consist of a freely rotating roller on which the shore rests at its front end. This roller is mounted on an independent support on which is pivoted the front end of a hydraulic cylinder, the back end of which is anchored by means of a corresponding pivot on the frame. This axis of articulation between the support and the cylinder is mounted between two lugs attached to the forward arch of the frame, with the ability to slide within two opposing slots in the said lugs, slots which define an upwardly inclined plane along which the axis of articulation slides under the action of the corresponding cylinder.
This construction permits the end section of the shore to be forced outward so as to exert a controlled pressure against the tunnel surface, and which facilitates, moreover, the forward movement of the structure.
The shores are actuated by means of an impulse cylinder mounted in collars attached to the shores, these cylinders articulating at their back end on lugs attached to the rear arch of the frame, which at their forward end are articulated on the shore.
The variations in the machine's section are obtained on the one hand by means of the above described elastic suspension and, on the other, by positioning the heads of the shores.
The means for guiding the skids in the vertical direction consist of a beam inside each skid composed of two pieces of equal length, mutually articulated about a horizontal axis. This axis is mounted between two lugs attached to the frame. Further, the two parts of the beam pivot at their free ends of the forward and rear arches of the frame by means of pivoting hydraulic cylinders. Each part of the beam is also provided with an upper, freely rotating roller on which the skid rests in such a way that on the one hand, the load-bearing structure rests on the skids by way of the rollers which form the elastic supports and, on the other hand, each skid rests on the guide beam by way of the upper rollers mounted on the beam.
Inside each skid there slides, in addition, two hydraulic jacks connected to the skid at one end and to the frame at the other, their purpose being the displacement of the rig in conjunction with the impulse cylinders of the shores.
With the described construction, the skids are always held in the same plane, avoiding excessive or uncontrolled displacement with respect to the frame and maintaining their relative positions.
Each pair of skids is connected together by an intervening anchoring beam. For this purpose, each pair of skids has longitudinal wings projecting from the bottoms of their opposed faces shaped so that they overlap over a portion provided with overlapping holes through which project teeth protruding from the bottom surface of the anchoring beam. The anchoring beam is articulated at its front end to the skid pair in which it is located by means of a transverse axis of rotation while on the top of its back end, it is connected to the load-bearing frame by way of a hydraulic cylinder. The anchoring teeth are long enough to dig into the tunnel floor and prevent the skids from sliding backwards when their advancing cylinders are actuated. During the advance of the skids, the cylinder of the anchoring beam is actuated so as to raise it and retract the teeth so that they do not impede the advance. By anchoring the teeth of the beams on one side of the frame and raising the beams on the other side, the direction of motion of the machine can be turned to the right or left.